Heterocyclic and aromatic based polyurethane scaffolds: morphology and crystallinity studied by X-ray diffraction, small-angle X-ray scattering and differential scanning calorimetry

The morphology, crystallinity and X-ray diffraction of speciality heterocyclic and aromatic based polyurethane and poly(urethane–urea) elastomers synthesized via a one-shot polymerization method were studied. The samples were chain extended by mixtures of aliphatic diols and furanic or aromatic diamine chain extenders. Small-angle X-ray scattering (SAXS) measurements confirmed the results obtained by differential scanning calorimetry (DSC) and revealed the presence of phases with sharp phase boundaries. The SAXS patterns are best fitted with a model that consists of liquid-like ordered polydisperse spheres. Most of the samples were shown to be poorly crystalline, but some soft-phase crystals do exist and these melted at about 353 K as confirmed by DSC and temperature-dependent wide-angle X-ray diffraction. Annealing at 273 K did not affect the thermal stability but influenced the morphology of the samples. The effect of annealing on the samples of poly(urethane–urea) extended using diamine chain extenders was smaller than that for polyurethane samples, which indicates a much higher thermal stability of the poly(urethane–urea) samples owing to the formation of bidentate hydrogen-bond networks across the urea groups.